The present invention relates to a Se-As system photosensitive material for use in electrophotography.
Generally speaking, up to now there have been widely used electrophotographic photosensitive materials of the type which comprises an electrically conductive substrate made from aluminum or the like and a photoconductive layer formed thereon by vacuum vapordepositing selenium or selenium system alloy on said substrate. This is because selenium system photosensitive materials exhibit collectively excellent characteristics such as, for instance, photoconductivity, durability and the like. Particularly, Se-As system photosensitive materials have attracted public attention because of their superior light sensitivity to light of the long wavelength region and the like.
In this regard, there are various factors that exert influence upon the characteristics of these photosensitive materials. Among them, however, it is the oxygen present as-dissolved in the raw materials therefor that exerts a most great influence upon said characteristics.
In other words, the more the dissolved oxygen that is present, the more the residual potential increases to thereby exert a great influence upon the copied image quality. Due to this, various steps such as, for instance, vacuum distillation and the like have been taken in order that the dissolved oxygen may be removed to the utmost.
It is surely preferable to take the aforesaid steps when the raw material for the preparation of the photosensitive material is pure Se or Se-Te system alloy.
However, when the raw material therefor has a composition resembling the Se-As system, in particular As.sub.2 Se.sub.3, the removal of said dissolved oxygen causes the charged potential tend to dissipate and even if charged successfully, it brings about an increase in the dark decay.
On the contrary, when the amount of said dissolved oxygen increases more than is needed, the photosensitive material is liable to fatigue, like the pure Se or Se-Te system photosensitive material, with the result that the residual potential increases. When a dissolved oxygen-rich alloy is vacumm vapordeposited, the resulting photosensitive material surface is liable to have projections and thus its outward appearance becomes poor.